It is narrated from al-Hasan (al-Basri) (may Allah have mercy on him) that the Prophet (peace and blessings be upon him) said: "The imam is a guarantor and the muezzin is entrusted; may Allah Almighty guide the imams and forgive the muezzins," or he said: "May Allah Almighty forgive the imams and guide the muezzins." Ibn Abi Adi was in doubt.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2030